Physiology D Nervous Student - Irene's · 10/4/18 2 Copyright © 2016 by Elsevier Inc. All...

10/4/18

Nervous System

Chapter 23

Introduction

• Nervous system uses transmitted electrical signals called impulses to relay messages and to stimulate change

• Body’s master communication and regulating system

• Every thought, action, and sensation reflects nerve activity

Anatomy

• Brain• Spinal cord• Cranial and spinal nerves• Sense organs• Neurotransmitters

Physiology

• Sensory input• Interpretive functions• Motor output• Higher mental functioning and

emotional responsiveness

Central Nervous System

• Interprets sensory information⎼ Issues instructions in the form of motor

responses• Governs thoughts and emotional

responses• Surrounded by bones of skull and spinal

column

Major Components of the Central Nervous System

• Brain • Spinal cord• Meninges• Cerebrospinal fluid (CSF)

10/4/18

Peripheral Nervous System

• Cranial nerves: Exit brain• Spinal nerves: Exit spinal cord• Subdivisions of PNS are:

⎼ SNS: Voluntary (responses consciously controlled)

⎼ ANS: Involuntary • ANS contains sympathetic and

parasympathetic divisions

Cells of the Nervous System

• Nervous system made up of billions of cells

• Two types: ⎼ Neurons⎼ Neuroglia

Neuroglia

• Supports, protects, and insulates neurons

• Smaller and more numerous than neurons⎼ Makes up more than 50% of CNS

Neuroglia

• Glial cells in CNS are:⎼ Astrocytes⎼ Microglia⎼ Oligodendrocytes

• Glial cells in PNS are:⎼ Schwann cells⎼ Satellite cells

Neurons

• Impulse-conducting cells • Properties include:

⎼ Excitability: Converts stimulus into impulse⎼ Conductibility: Transmits impulses to

neurons, muscles, and glands⎼ Secretion: Secretes neurotransmitters

Parts of a Neuron

• Cell body⎼ Contains nucleus and other organelles

• Dendrite⎼ Transmits impulses to cell body

• Axon⎼ Transmits impulses away from cell body

10/4/18

Myelin

• Insulation• Speed conduction

Functional Classification of Neurons

• Afferent (sensory): Carry impulses to CNS

• Efferent (motor): Carry impulses from CNS to muscles or glands

• Interneurons (association): Carry impulses between sensory and motor neurons and perform integrative functions

Connective Tissue Layers of Nerves

• Epineurium⎼ Outer layer around entire nerve

• Perineurium⎼ Surrounds fascicles

• Endoneurium ⎼ Surrounds individual neurons and their

extensions

Nerve Impulses

• Electrical signals that convey information along neurons

• Action potential• Change in the electrical charge of a cell

membrane ⎼ Needed to conduct an impulse⎼ Caused by movement of charged particles

(ions)

Sodium-Potassium Pump

• Produces and maintains polarization• Pumps ions in opposite directions at an

unequal rate• Ions are:

⎼ Sodium (Na+)⎼ Potassium (K+)

All-or-None Response

• Impulse is conducted along entire neuron at maximum capacity⎼ No fluctuations or decrease in magnitude

• Impulse continues until it reaches end of neuron

10/4/18

Refractory Period

• Inability of a neuron to conduct another impulse ⎼ Essentially, a neuron's unresponsive

period

Synapse

• Junction between:⎼ Neuron and neuron⎼ Neuron and muscle⎼ Neuron and gland

• Impulses are transmitted across synapse by with help of neurotransmitters

Synaptic Structures

• Synaptic bulbs ⎼ Located at end of axon⎼ Contain neurotransmitters

• Synaptic gap (cleft)⎼ Space between synaptic bulb and plasma

membrane

Neurotransmitters

• Chemical messengers involved in synaptic transmission

• Stored in vesicles of presynaptic neuron• Can be excitatory or inhibitory

Examples of Neurotransmitters

• Acetylcholine is most common• Epinephrine and norepinephrine• Serotonin• Dopamine• Endorphins

Central Nervous System

• Brain and spinal cord• Protected by

⎼ Skull ⎼ Vertebral column⎼ Meninges⎼ Cerebrospinal fluid (CSF)

10/4/18

• It interprets sensory information and governs intellectual activity, consciousness, memories, and emotions

• Uses glucose as an energy source⎼ Cerebrum⎼ Diencephalon⎼ Cerebellum ⎼ Brainstem

Cerebrum

• Largest area of brain• Language centers interpret

written/spoken words as well as speech• Cerebral cortex covers outer region of

cerebrum⎼ Sulci and gyri separate cerebrum into

Cerebral Hemispheres

• Cerebrum contains right and left hemispheres ⎼ Research indicates they possess

specialized functions• Longitudinal fissure

⎼ Separates hemispheres• Corpus callosum

⎼ Transverse fibers connecting hemispheres

Hemispheric Specialization

• Left hemisphere

⎼ Language: Receptive and expressive

⎼ Governs many mathematical abilities, as

well as reasoning and analytical skills

• Right hemisphere specializes in sounds

⎼ Melodies

⎼ Art

⎼ Emotional expression

⎼ Spatial relationships

Cerebral Lobes

• Frontal lobe⎼ Motor function⎼ Personality/mood⎼ Intellect ⎼ Speech

• Parietal lobe⎼ Sensation ⎼ Speech⎼ Understanding

Cerebral Lobes

• Temporal lobe⎼ Auditory ⎼ Naming⎼ Memory

• Occipital lobe⎼ Vision ⎼ Whole object integration

10/4/18

Brain Waves and States of Consciousness

• Consciousness: Degree of mental alertness and responsiveness

• Levels of consciousness recorded as brain wave patterns⎼ Beta⎼ Alpha⎼ Theta⎼ Delta

Brain Wave Patterns

• Beta⎼ Wakeful consciousness and mental activity⎼ High-intensity waves are associated with

extreme stress• Alpha

⎼ Awake and relaxed

Brain Wave Patterns

• Theta⎼ Drowsiness and dreamlike awareness,

subconscious, out-of-body experiences• Delta

⎼ Deep sleep from which the subject is not easily aroused

Diencephalon

• Located in center of brain• Contains two primary structures:

⎼ Thalamus ⎼ Hypothalamus

Thalamus and Hypothalamus

• Thalamus

⎼ Relays sensory information (except

olfaction) to appropriate parts of cerebrum

• Hypothalamus

⎼ Regulates ANS

⎼ Controls hunger and thirst, anger and

aggression, hormones, sexual behavior,

and sleep patterns

Cerebellum

• Located posterior and inferior to cerebrum⎼ Concerned with muscle tone⎼ Coordinates complex muscular movements⎼ Regulates posture and balance

10/4/18

Brainstem

• Vegatative function• Continuous with spinal cord • Three divisions:

⎼ Midbrain⎼ Pons⎼ Medulla oblongata

Midbrain and Pons

• Midbrain⎼ Conducts nerve impulses from cerebrum to

pons ⎼ Conducts sensory impulses from spinal

cord to thalamus• Pons

⎼ Connects cerebellum and cerebrum with spinal cord

Medulla Oblongata

• Transmits sensory and motor impulses between brain and spinal cord

• Contains: ⎼ Respiratory center⎼ Cardiovascular center⎼ Vasomotor center

Spinal Cord

• Exits skull via foramen magnum • Integrating center and information

highway• Cauda equina

⎼ Lower portion of cord fans out like a horse tail

Spinal Cord

• Cross section reveals:⎼ White matter: Located on periphery⎼ Gray matter: Located in deeper regions

• H-shaped

• Central canal⎼ Center of spinal cord; contains circulating

Spinal Cord: Tracts

• Two types: ⎼ Ascending

• Sensory (afferent) impulses travel up cord⎼ Descending

• Motor (efferent) impulses travel down cord

10/4/18

Meningeal Layers

• Pia mater⎼ Innermost delicate layer⎼ Attaches to surface of CNS

• Arachnoid⎼ Middle layer; forms loose covering around

CNS• Dura mater

⎼ Outermost dense layer; lies against bones of CNS

Cerebrospinal Fluid

• Fluid circulating around brain and spinal cord

• Functions include:⎼ Supplies oxygen and nutrients to tissues of

brain and spinal cord⎼ Removes metabolic waste during sleep⎼ Acts like a shock absorber

Peripheral Nervous System

• Cranial nerves⎼ Arise from inferior surface of brain⎼ 12 pairs

• Spinal nerves⎼ Arise from spinal cord ⎼ 31 pairs

Cranial Nerves

• CN I: Olfactory - smell• CN II: Optic - sight• CN III: Oculomotor - eye movement• CN IV: Trochlear - eye movement• CN V: Trigeminal - face sensation and

chewing • CN VI: Abducens - eye movement • CN VII: Facial - facial expression

Cranial Nerves

• CN VIII: Vestibulocochlear - hearing and equilibrium

• CN IX: Glossopharyngeal - oral sensation, taste and salivation

• CN X: Vagus - 90% of parasympathetic nervous system

• CN XI: Accessory (spinal accessory) -trapezius and SCM

Spinal Nerves

• 31 pairs⎼ 8 cervical nerves ⎼ 12 thoracic nerves⎼ 5 lumbar nerves⎼ 5 sacral nerves⎼ 1 coccygeal nerve

10/4/18

Structure of Spinal Nerves

• Part of spinal nerve that connects to spinal cord

• Two types:⎼ Ventral (anterior)

• Contains motor neurons⎼ Dorsal (posterior)

• Contains sensory neurons

Ganglion

• Cluster of nerve cell bodies • Ventral and dorsal roots merge to form

a single nerve

Nerve Plexuses

• Network of intersecting nerves in PNS• Major plexuses:

⎼ Cervical⎼ Brachial⎼ Lumbosacral

Dermatomes

• Area of skin supplied by specific sensory nerve root

• Dermatomes are named by their corresponding nerve

• Distribution called a dermatome map⎼ Each map has its own variations

Myotomes

• Group of skeletal muscles supplied by specific motor spinal nerve root

• Distribution is called a myotome map• Sometimes used in muscle tests

Reflexes

• Involuntary and predictable• Cranial reflex means the brain mediated

the reflex⎼ Primitive reflexes may reappear in people

with dementia• Spinal reflex means the spinal cord

mediated the reflex

10/4/18

Autonomic Nervous System

• Innervates cardiac and smooth muscles/glands, thus regulating:⎼ Heart and respiration rates⎼ Blood circulation⎼ Body temperature⎼ Gastrointestinal activity and metabolism

• Two divisions: ⎼ Sympathetic and parasympathetic

Dual Innervation

• Innervated by both sympathetic and parasympathetic divisions

• Some have only sympathetic innervation ⎼ Example: Adrenal glands

• Some have only parasympathetic innervation ⎼ Example: Lacrimal apparatus

Parasympathetic Division

• Supports functions that conserve and restore energy

• Regulates digestion⎼ "Housekeeping" division

• Nerves emerge from the brainstem and sacrum

Sympathetic Division

• Dominates during physical exertion or emotional stress⎼ Effects include raises in heart rate, blood

pressure, and respiration• Suppresses activity of the digestive and

urinary systems• Also called the thoracolumbar division

• Many different types of many receptors, such as: ⎼ Pressure⎼ Movement⎼ Temperature⎼ Nociception and pain perception

• Chemoreceptors activated when a molecule from a particular size and shape fits into a particular receptor site

• Five primary tastes:⎼ Salty⎼ Sweet⎼ Bitter⎼ Sour⎼ Savory

• Strongly influenced by smell60

10/4/18

• Olfaction: Sense of smell• Scent receptors located in superior

nasal cavity⎼ Molecules fit into receptor sites;

information travels into olfactory bulb and the brain

• Plays important role in sexual behavior

Vision

• Photoreceptors transmit visual information and send to retina

• Rods are active in dim light, responsible for night vision

• Cones are active in bright light, specialized for detecting color

Hearing

• Mediated by mechanoreceptors ⎼ Detect sound waves and vibrations

• Sound waves vibrate tympanic membrane, causing it to vibrate⎼ Transmitted through three small bones in

middle ear• Oval window covers opening to cochlea

⎼ Sound waves travel until they reach brain

Balance and Equilibrium

• Fluid-filled canals contain mechanoreceptors that resemble hair⎼ These cells move when we move⎼ Information is sent along nerves, notifying

brain of body movements

Receptors

• Respond to stimuli by creating a nerve impulse⎼ Our bodies avert harm and seek nourishment

• Specific receptors generally detect specific stimuli

• Perception: Organization, identification, and interpretation of sensory information

• Adaptation: Decrease in sensitivity to prolonged stimulus

Proprioceptors

• Found in muscles, joints, fascia, and ears

• Detect body movements, body position, and muscle stretch

10/4/18

Receptors Classified by Type of Stimuli Detected

• Chemoreceptors detect chemical stimuli or changes in chemical concentrations of fluids

• Nociceptors detect noxious stimuli, such as excessive heat and cold or tissue damage

• Mechanoreceptors detect mechanical stimuli

Muscle Spindles

• Stretch receptors wrapped around intrafusal fibers

• Monitor changes in muscle length and rate of change

• Cause reflexive contraction when muscles are overstretched

Golgi Tendon Organs

• Activated by muscle tension • Located at musculotendinous junctions• If tension is too great, motor efferent

neurons are inhibited ⎼ Causes inverse stretch reflex

Physiology D Nervous Student - Irene's · 10/4/18 2 Copyright © 2016 by Elsevier Inc. All...

Documents

Spinal Nerves and Autonomic Nervous System

Nervous System Peripheral Nervous System AutonomicSympathaticParasympatheticSomatic NervesSensory NervesMotor Nerves Central Nervous System Nerves that

The Peripheral Nervous System (PNS ) Spinal Nerves

The Peripheral Nervous System. Peripheral Nervous System 31 pairs of spinal nerves 12 pairs of cranial nerves All of the smaller nerves that branch from

+ Peripheral Nervous System. + PERIPHRAL NERVOUS SYSTEM PNS LIES OUTSIDE THE CENTRAL NERVOUS SYSTEM COMOSED OF NERVES NERVES = BUNDLES OF AXONS WE CALL

Peripheral Nervous System Nerves outside the brain

Nervous System. The entire nervous system is composed of nerves

Central Nervous System - Spinal Cord, Spinal Nerves

Peripheral Nervous System Cranial Nerves Cranial Nerves Spinal Nerves Spinal Nerves Reflex Activity Reflex Activity Autonomic Nervous System Autonomic

Peripheral nervous system Nervous system. Peripheral nervous system Nerves that branch from CNS and connect it to other body parts Cranial nerves Arise

Central Nervous System, Spinal Nerves, and Cranial Nerves Physiology... · Central Nervous System, Spinal Nerves, and Cranial ... Nerves attached to spinal cord by 2 roots ... Both

Nervous System - University of Arizona · - spinal cord • Peripheral Nervous System (PNS) - cranial nerves - spinal nerves - autonomic nerves ... - Highest nervous correlation

NERVOUS SYSTEM · cranial nerves spinal nerves ganglia peripheral nerves enteric plexuses sensory receptors. Overview of the Nervous System Central nervous system-CNS Brain & Spinal

Brain Structure 02.04.2016. Nervous System Central Nervous System BrainSpinal Cord Peripheral Nervous System Cranial nerves, spinal nerves, peripheral

Nervous System Intro Nerves

The Visceral Nervous System. Composition Visceral motor nerves (autonomic nervous system) Sympathetic part Parasympathetic part Visceral sensory nerves

Anatomy 18.1-Peripheral-nervous-system cranial-nerves

Nervous Development - Biology Courses Servercourses.biology.utah.edu/nielsen/ewExternalFiles/14...Peripheral nervous system Cranial nerves Spinal nerves Autonomic nervous pathways

Peripheral Nervous System Classification of Nerves

Overview of the Central Nervous System - …. The Nervous System has Peripheral and Central Divisions. Peripheral Nervous System • all spinal, cranial nerves • all autonomic nerves